A strong indication of the reliability of Chandrasekhar's formula is that the absolute magnitudes of supernovae of Type Ia are all approximately the same ; at maximum luminosity, M < sub > V </ sub > is approximately-19. 3, with a standard deviation of no more than 0. 3 .< sup >, ( 1 )</ sup > A 1-sigma interval therefore represents a factor of less than 2 in luminosity.

Type II Cepheids ( historically termed W Virginis stars ) have clock regular light pulsations and a luminosity relation much like the δ Cephei variables, so initially they were confused with the latter category.

Comparing the light curve, the amplitude and the radial velocity variations as compared to the light curve, Type II Cepheids constitute a different class of star with a luminosity relation offset from that of the δ Cepheids.

A Type I X-ray burst has a sharp rise followed by a slow and gradual decline of the luminosity profile.

Type IIn supernovae are all embedded in a dense nebula probably expelled from the progenitor star itself, and this circumstellar material ( CSM ) is thought to be the cause of the extra luminosity.

These include estimates based on data from Baryon Acoustic Oscillations and Type Ia supernova luminosity / time dilation measurements.

Another dimension that is included in the Morgan-Keenan system is the luminosity class expressed by the Roman numbers I, II, III, IV and V, expressing the width of certain absorption lines in the star's spectrum.

Apart from this, because of their large radii and luminosities, giant stars lie above the main sequence ( luminosity class V in the Yerkes spectral classification ) on the Hertzsprung – Russell diagram and correspond to luminosity classes II or III.

In collaboration with Vainu Bappu, an Indian astronomer, he also showed that there was a correlation between the width of the Ca II lines in stellar spectra and the star's luminosity, the Wilson-Bappu Effect.

Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other type II supernovae but did resemble the variations observed in type Ib supernovae.

The estimated age of this star is 420 million years and it has evolved away from the main sequence to become a giant star with a spectral classification of K3 and luminosity class between II and III.

Bright giant stars are stars of luminosity class II.

showing that the lower luminosity group are post-red supergiant stars with masses of 30 – 60 times the sun, while the higher luminosity group are population II stars with masses 60 – 90 times the sun which never develop to red supergiants although they may become yellow hypergiants.

The ' II ' luminosity class is for a bright giant star that has exhausted the hydrogen at its core and has followed an evolutionary track away from the main sequence of stars like the Sun.

Epsilon Leonis has a stellar classification is G1 II, with the luminosity class of II indicating that, at an age of, it has evolved into a bright giant.

The luminosity class II in the Yerkes spectral classification is given to bright giants.

Either component is of the spectral type G through K and luminosity class II through IV.

Cepheids have been shown to have a relationship between their absolute luminosity and the period over which their brightness varies.

* Cepheids and cepheid-like stars They have short periods ( days to months ) and their luminosity cycle is very regular ;

A relationship between the period and luminosity for classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt in an investigation of thousands of variable stars.

The strong direct relationship between a Cepheid variable's luminosity and pulsation period secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.

A relationship between the period and luminosity for classical Cepheids was discovered in 1908 by Henrietta Swan Leavitt in an investigation of thousands of variable stars in the Magellanic Clouds.

The luminosity of the water is now believed to have been caused by the stimulation of vast numbers of the luminescent organism Noctiluca miliaris by the turbulence of the sea.

The absolute magnitude is then equivalent to the apparent magnitude an object would have if it were at a standard luminosity distance ( 10 parsecs ) away from the observer, in the absence of astronomical extinction.

Bolometric magnitude is luminosity expressed in magnitude units ; it takes into account energy radiated at all wavelengths, whether observed or not.

For galaxies ( which are of course themselves much larger than 10 parsecs, and whose overall brightness cannot be directly observed from relatively short distances ) the absolute magnitude is defined by reference to the apparent brightness of a point-like or star-like source of the same total luminosity as the galaxy, as it would appear if observed at the standard 10 parsecs distance.

where is the star's luminosity distance in parsecs, wherein 1 parsec is approximately 3. 2616 light-years.

For nearby astronomical objects ( such as stars in our galaxy ) luminosity distance D < sub > L </ sub > is almost identical to the real distance to the object, because spacetime within our galaxy is almost Euclidean.

For much more distant objects the Euclidean approximation is not valid, and General Relativity must be taken into account when calculating the luminosity distance of an object.

Bolometric magnitude corresponds to luminosity, expressed in magnitude units ; that is, after taking into account all electromagnetic wavelengths, including those unobserved due to instrumental pass-band, the Earth's atmospheric absorption, or extinction by interstellar dust.

Its visual luminosity is about 10, 000 times that of the Sun, but because the star radiates a considerable part of its energy in the infrared part of the spectrum, the bolometric luminosity equals roughly 65, 000 times that of the Sun.

At magnitude 5. 5, it is only 1 / 370th as bright visually as Antares A, although it shines with 170 times the Sun's luminosity.

Altair is a type-A main sequence star with approximately 1. 8 times the mass of the Sun and 11 times its luminosity.

Another method is to measure the brightness of an object and assume an intrinsic luminosity, from which the distance may be determined using the inverse square law.

The candela ( or ; symbol: cd ) is the SI base unit of luminous intensity ; that is, power emitted by a light source in a particular direction, weighted by the luminosity function ( a standardized model of the sensitivity of the human eye to different wavelengths, also known as the luminous efficiency function ).

where I < sub > v </ sub >( λ ) is the luminous intensity in candelas, I < sub > e </ sub >( λ ) is the radiant intensity in W / sr and is the standard luminosity function.

* Contrast ratio is the ratio of the luminosity of the brightest color ( white ) to that of the darkest color ( black ) that the monitor is capable of producing.

Active galaxies that emit high-energy radiation in the form of x-rays are classified as Seyfert galaxies or quasars, depending on the luminosity.

The MK classification assigned each star a spectral type — based on the Harvard classification — and a luminosity class.

This line is pronounced because both the spectral type and the luminosity depend only on a star's mass, at least to zeroth order approximation, as long as it is fusing hydrogen at its core — and that is what almost all stars spend most of their " active " lives doing.

As the position of a star on the HR diagram shows its approximate luminosity, this relation can be used to estimate its radius.

The ratio of M to R increases by a factor of only three over 2. 5 orders of magnitude of M. This relation is roughly proportional to the star's inner temperature T < sub > I </ sub >, and its extremely slow increase reflects the fact that the rate of energy generation in the core strongly depends on this temperature, while it has to fit the mass – luminosity relation.

The huge luminosity of quasars results from the accretion discs of central supermassive black holes, which can convert on the order of 10 % of the mass of an object into energy as compared to 0. 7 % for the p-p chain nuclear fusion process that dominates the energy production in sun-like stars.

Although stellar parameters can be expressed in SI units or CGS units, it is often most convenient to express mass, luminosity, and radii in solar units, based on the characteristics of the Sun:

A Hertzsprung – Russell Diagram can be plotted for these clusters which has absolute values known on the luminosity axis.

In the current system of stellar classification, stars are grouped according to temperature, with the very young and energetic Class O stars boasting temperatures in excess of 30, 000K while the older Class M stars exhibit temperatures less than 3, 700K — a vast difference that has a huge impact on the star's luminosity.

Their luminosity is directly related to their period of variation, with a slight dependence on metallicity as well.

The spectrum of this star matches a stellar classification of, with the luminosity class of III indicating that it is an evolved giant star that has exhausted the supply of hydrogen at its core and is now on the red giant branch.

Several color solids before Munsell ’ s plotted luminosity from black on the bottom to white on the top, with a gray gradient between them, but these systems neglected to keep perceptual lightness constant across horizontal slices.

The Tully-Fisher relation shows for spiral galaxies that rotation is related to galaxy luminosity, which in turn is dependent on the amount of matter in the stars of the galaxy.

The luminosity is variable at nearly every wavelength from radio waves to Gamma rays on timescales of a few days to decades.

Astronomers who believed quasars were not at cosmological distances argued that the Eddington luminosity set limits on how distant the quasars could be since the energy output required to explain the apparent brightness of cosmologically-distant quasars was far too high to be explainable by nuclear fusion alone.

In that situation the mass of the neutralizing positive charge carriers is nearly 1836 times smaller ( the proton to electron mass ratio ), while the radiation pressure on the positrons doubles the effective upward force per unit mass, so the limiting luminosity needed is reduced by a factor of ≈ 1836 / 2 = 918.

The exact value of the Eddington luminosity depends on the chemical composition of the gas layer and the spectral energy distribution of the emission.

For accretion powered sources such as accreting neutron stars or cataclysmic variables ( accreting white dwarfs ), the limit may act to reduce or cut off the accretion flow, imposing an Eddington limit on accretion corresponding to that on luminosity.

The Eddington limit is not a strict limit on the luminosity of a stellar object.

In this first phase of the simulation we see that black daisies have warmed Daisyworld so that it is habitable over a wider range of solar luminosity than would have been possible on a barren, gray planet.

The relationship between the luminosity emitted in the rest frame of the jet and the luminosity observed from Earth depends on the characteristics of the jet.